Process for producing cyanoethylated native cotton fibers by reacting cellulose fibers with acrylonitrile in vapor phase



March 26, 1957 J COMPTON ETAL 2,786,735

PROCESS FOR PRODUCING CYANOETHYLATED NATIVE COTTON FIBERS BY REACTING CELLULOSE. FIBERS wrra ACRYLONITRILE IN VAPOR PHASE Filed June 10, 1954 INVENTORS -JACK COMPTON BY CATESBY P. JONES ATTORNEYS United States Patent PROCESS FOR PRODUCING CYANOETHYLATED NATIVE COTTON FEERS BY REACTING CEL- LULOSE FBERS WITH ACRYLONITRILE IN VAPOR PHASE Jack Compton, Charlottesville, Va., and Catesby P. Jones,

Bethesda, Md., assignors to Institute of Textile Technology, Charlottesville, Va., a corporation of Virginia Application June 10, 1954, Serial No. 435,003

9 Claims. (Cl. 8-120) This invention relates to the reaction of acrylonitrile with cotton and has for its object the provision of improved cotton products and a process of reacting acrylonitrile with cotton fibers in the form of bulk fibers, yarns, or fabrics to improve the properties of the cotton While maintaining the natural structure of the fiber and most of the properties of ordinary cotton. Our invention provides an economical and practical process of producing our improved cotton products with a minimum loss of chemicals through washing, neutralizing and undesirable by-product formation. The improved cotton products of our invention are a partially cyanoethylated cotton, but they have the important distinction of retaining the natural fibrous form of native cotton fibers, and their crystallinity in a substantially unaltered state.

Several processes have been proposed heretofore for treating cellulose with aqueous solutions of sodium hydroxide and acrylonitrile to effect from a partial to a complete cyanoethylation, usually resulting in a soluble product, but, in any event, resulting in a product having a materially changed physical structure. Notwithstanding a considerable number of patents and other publications concerning the cyanoethylation of cotton and regenerated cellulose, namely rayon, there has not been any commercially successful process developed heretofore.

Our invention is based on several important discoveries we have made in an extensive investigation of the cyanoethylation of cotton through which me may control the conditions for reacting acrylonitrile, CH2=CH2CN, with but a relatively small proportion of the cellulose giving cyanoethylcellulose which may be represented as We have found that very desirable cotton products can be formed by effecting but a partial etherification of the cellulose molecule, resulting in but from 0.06 to 1.0 cyanoethyl group per anhydro-glucose unit (equivalent to from 0.50 to 6.50% nitrogen based on the weight of cyanoethylated cotton). In the preferred and most advantageous embodiment of our invention, we control the conditions to combine but from 0.1 to 0.6 cyanoethyl groups per anhydro-glucose unit.

The following table shows the relationship between the cyanoethyl groups per anhydro-glucose unit and the nitrogen content of the cyanoethylated cotton:

ice

2 TABLE A ydro- Glucose Unit Percent N Our invention is specifically directed to the treatment of native cotton because we aim to produce an improved cotton fiber and cotton is peculiarly suited to our process. While cotton is a relatively pure form of cellulose, the fibers are considered to be formed of three distinct types of layers each having a difierent physical structure, consisting of amorphous and crystalline components. Mild reaction conditions, such as the preferred cyanoethylation procedure herein described, are required to maintain this desirable fiber structure. In particular the relationship between the amorphous and crystalline components should be maintained. One further characteristic of cotton is that the degree of polymerization varies from about 1500 to 4500 and in this respect it differs from viscose rayon which has a degree of polymerization of from about 150 to 450. In general, all regenerated cell-ulosic fiber materials have a greater proportion of the amorphous component than native cotton and the crystalline component is characterized by having the mercerized cellulose molecular arrangement. Cotton thus has a difierent structural arrangement and responds differently than regenerated cellulose when treated with such chemicals as sodium hydroxide and acrylonitrile. Because of its structure, cotton is a very important textile material and our process maintains its structural identity.

We have discovered a very important relationship involving the concentration of sodium hydroxide in the steeping solution for treating the cotton prior to cyanoethylation, the amount of sodium hydroxide fixed to or combined with the cellulose, and the time and temperaations necessary in the process.

Not only is the saving in sodium hydroxide an appreciable item but the saving in the neutralizing acid required in the process is also an important item.

In addition to an important saving in chemicals, the fibers of cotton are reacted under controlled conditions of time and temperature to effect the desired reaction to fix a definite amount of acrylonitrile on the cotton and thus maintain its natural fibrous character and internal molecular arrangement with an improvement in its utility as a cotton-like fiber.

The manner in which we treat the cotton with sodium hydroxide is a very important part of our invention because the cyanoethylation cannot give satisfactory results unless there has been a relatively uniform application of sodium hydroxide to all the fibers thereby leaving on the fibers, whether combined or sorbed, a predetermined amount of sodium hydroxide,"and to this end we prefer to use a dilute solution of sodium hydroxide, in no event more concentrated than %,preferablybelow 2% and It is accordingly necessary to avoid the use of strong caustic solutions (say over 10% NaOH) since the presence of such solutions tend to hydrolyze the nitrile -CN to carboxyl COOH and significantly increase the proportion of the amorphous fiber component. It is particularly advantageous, therefore, to avoid the use of concentrations of sodium hydroxide which cause these changes in the cyanoethylated product and its precursor.

We havefound that in order to preserve the fibrous character of the cotton and form only a small portion of cyanoethylcellulose that uniformityof sodium hydroxide treatment is necessary and we can best achieve the desired uniformityby treating the cotton with a large volume of dilute solution rather than with a small volume of strong solution objectively to treat all fibers alike. It is definitely. advantageous to use ardilutesolution of sodium hydroxide and to sorb on the cottorrfrom 1.5 to 22 milligrams of sodium hydroxide ,per gram of cotton.

Our invention provides improved cotton products derived from native cotton characterized by having the amorphous portion of the fibers combined with acrylonitrile in the form of cyanoethylcellulose while. substantially all of the crystalline structurepf the cot-ton fiber is retained. The amorphous portion has such an amount of combined acrylonitrile that the nitrogen content of the entire fiber varies from 0.50 to.6 .5-%.

Thepartially cyanoethylated cotton fibersof our invention are similar in appearance, hand, and processing characteristics to cotton, but idifierprimarily and significantly in that they are permanently resistant to microorganism attack, such as cause mildew; more resistant to wet and dry heat degradation; more receptive to many dyes of all classes, including acid dyes; and more resistant to abrasion.

One of the features found in our investigations is that the amount of sodium hydroxide sorbed'takes place in a very few minutes and that longer contact does not add appreciable amounts. Based on the amountof available sodium hydroxide in the solution, the actual sorption is a functionof the sodium hydroxide in-the liquor and there is about as much sodium hydroxide sorbed in fifteen minutes as. in thirty minutes.

a In our copending application, Serial No.- 442,762,.filed July 12, 1364, we describe .and claim ,our improved fibrous cotton product, and a process for treating cotton fibers with aqueous solutions of sodium' hydroxide, preferably in a steeping process, and under the conditions described herein, but in the process of that application the presteeped cotton fibers are treated with liquid acrylonitrile containing some Water, whereas in this process the presteeped cotton fibers are treated with acrylonitrile in the vapor phase giving the advantage of simple and effective control of the reaction.

The cotton impregnated with sodium hydroxide solution in a presteeping treatment is treated to remove substantially all of the adhering solution as by centrifuging, for example, until the weight of the presteeped cotton is about double the Weight of the untreated cotton. Acrylonitrile vapor is then applied to the cotton at a temperature of from about 46 C. to 85 C., and preferably at a temperature around the boiling point of the acrylonitrile which is about 76 C. under atmospheric pressure. At temperatures above the boilingpoint of acrylonitrile the treatment-willabecarried out under pressure. Theiextent of :cyanoethylation increases with the amountof sodium hydroxide sorbe'd on the cotton. The rate-of cyanoethylation also increases with an increase in temperature, other factors being equal. In: producing our products the temper-attireof'acrylonitrile'and the time of treatment must be observed inrelation to the sodium hydroxide con-tent of the cotton toacquire the desired cyanoethylation. Our invention provides a process for controlling cyanoethylation to prevent an undue substitution of cyanoethyl groups Witha material saving in chemicals, in a relatively short time,to selectively 'cyanoethylate the amorphous portion of the fibers, resulting in superior cotton-like fiber products. 7

'ln achieving the important resistance to degradation by mildew-causing organisms we do not appreciably change the physical properties of the fibers, and unlike the proposed practices published heretofore we avoid deteriorationin strength resulting from the higher degrees of substitution and also'impart heat resistance to the cotton. 'Moreover, we obtain products having superior resistance to mildew.

In carrying out a process of our invention, the cotton fibers with so'rbed sodium hydroxide as previously described is then exposed to the vapor for but a few minutes, say, from 1.5 to minutes, but not more than 4 hours, tocause the desired substitution of from 0.1 to 0.6 cyanoethylgroups per anhydro-glucose unit. The reaction may be carried out in any suitable equipment. One satisfactory arrangement comprises a chamber for the gas through which the .cotton may be continuously passed having closure means whereby the cotton may enter and leave to minimize the loss of vapor, and means to supply vapor to the chamber continuously. This may be done by evaporating the liquid aclylonitrile and passing the vapor into the chamber. In carrying the operation out at atmospheric pressure, upright pipes may be attached to the chamber and provided-with cooling means to condense the vapors thereinand. return the condensate to the body of liquidas in refluxing operations.

in the zaccompanyingdrawings:

Fig 1 illustrates more or less diagrammatically an arrangement of apparatus suitable for carrying out a process of the invention, and

Fig. 2 is an:enlarged vertical sectional-view taken within the area of the broken lines of Fig. l.

The apparatus illustrated in the drawings utilizes some of-the principlesof the St-andfast molten-metal machine which has been used for the dyeing of cotton. The app-aratus comprises a vessel 1 for holding the steeping solution of sodium hydroxide and guide rolls 2, 3 and 4 to provide along travel. The leg 5 of the U-shaped vessel U connects to the vessel 1 while the leg 6 connects to'the closedxvessel 7. The bottom cross-connectors has a drain valve--9and-a well for.thetherm'oregulator 10. The U- shapfid vessel maybe heated externally in any suitable 3 way as with an electrical resistance heater controlled by the thermoregulator and may be covered with thermal insulation.

The vessel 7 has a pan or pot 1 1 at the bottom for receiving liquid acrylonitrile with or without some water and it may be heated with any suitable means to boil the acrylonitrile and fill the chamber of vessel 7 with vapor. Preferably commercial acrylonitrile which contains some water is used, and this solution is boiled at the temperature of the azeotrope, or constant boiling mixture, which is about 71 to 72 C. The water-jacketed condenser 12 is open to the atmosphere and is positioned to return condensate to the pan 11. The chamber has direction guide rolls 13, 14, 15 and 16 to provide the required travel for the cotton, the roll 13 being directly over leg 6 and roll 16 being directly over leg 20 of U-shaped vessel U". The cross connector 21 has a drain valve 22 and a well for the thermoregulator 23. This U-shaped vessel may be heated with an electrical resistor and the temperature controlled with the thermoregulator 23. The leg 24 conmeets to washer 26 in which are mounted several guide rolls R to provide a long travel through the acid sour or hot water W, as the case may be.

The apparatus illustrated had U-shaped vessels of circular cross-section formed of pipe for treating yarn or cord; however, these vessels may be rectangular in crosssection for treating fabrics. The legs of U-sh-aped vessel U were 9 inches long and the legs of U-shaped vessel U" were 12 inches long and both were filled to the level indicated with Woods metal having a melting point of about 70 C. Any alloy having a suitable melting point that is non-reactive with caustic and acrylonitrile can be used in these vessels.

In carrying out a process of the invention, the cotton yarn or fabric C is run through the caustic, say, a 0.25% to.l% sodium hydroxide solution B at 45 to 50 C., which solution rests on the metal M in leg which is maintained at about 75 C. As the cotton passes through the metal in U-shaped vessel U, it is both heated to effect the reaction and squeezed to remove much of the excess solution. The acrylonitrile vapor V in the vessel is at refluxing temperature, about 71 to 72 C., and this vapor is in contact with the metal M in leg 6. On the other side, the vapor V is in contact with the metal M in leg 20. The metal M in leg 24 is in contact with the sour solution or hot wash water W in washer 26. The cotton passes through vessel 7 and then through the molten metal in U- shaped vessel U" in which a further extent of the reaction with acrylonitrile adhering to the cotton is carried out, and then the cotton passes through the washer 26 where it is neutralized, if desired, washed, and then dried as a finished article.

Example I In this example of an operation carried out in the apparatus of Fig. l, a cotton cord of 22/5/ 3 construction was run through the equipment at a speed of 1' yard per minute, using a 2% sodium hydroxide solution at 45 to 50 C. and an acrylonitrile vapor at 71 to 72 C. After the cord passed through the caustic steeping solution and the hot metal in legs 5 and 6, it passed through the vapor in chamber 7, the time being determined in part by the number of rolls and the length of travel they provide. In this example, the cotton was exposed to acrylonitrile vapor for about 1 /2 minutes.

The cord, after impregnation with acrylonitrile, passed through the molten metal in U-shaped vessel U, the legs of which are of such length as to remove as much acryl on-itrile as possible by pressure. At the same time, the temperature in this vessel can be regulated so that the residual acrylonitrile reacts with the cellulose. The process should drive the acryl-onitrile into the fiber and yarn structure.

After reaction with acrylonitrile, the cord passed from leg 24 of U shaped vessel U", practically free of this material, into an acid sour containing 0.5% H2804 at 55 to 60 C. in vessel 26. The sour wash may be omitted and the cord merely washed in hot water washer at to C. The vapor from this hot water washer is carried to any suitable recovery tower to recover acrylonitrile. Upon analysis, the cord was found to contain 0.62% nitrogen.

The yarn or fabric, after souring and washing thoroughly, is dryed and packaged.

This operation may be modified by charging the vessel 7 with liquid acrylonitrile instead of the vapor, and the speed of treatment may be regulated by the speed of travel of the cotton yarn or fabric and the length of travel in the various vessels.

Example 11 This is an example of another treatment of cotton fibers according to the invention in which the steeped cotton fabric was passed through a chamber containing acrylonitrile vapor.

Indian Head cotton fabric was steeped in a 2% solution sodium hydroxide for five minutes at room temperature and then centrifuged to a increase in weight. The fabric was then rolled up and pulled through a chamber of hot acrylonitrile vapor at such a rate that all parts of the fabric were uniformly exposed for a period of 2 /2 minutes. The acrylonitrile vapor was obtained from a boiling solution contained in a vessel attached to the reaction chamber. Reflux condensing means were attached to the chamber to condense vapors that would otherwise escape. The temperature of the acrylonitr-ile vapor was maintained at the boiling point which, in the presence of some water, may vary from 71 to 76 C., since the reflux condensers returned the condensate to the vessel. The fabric was shielded from the cold acrylonitrile condensate by a bafiie.

The partially cyanoethylated cotton fabric was then thoroughly washed with hot water to remove excess caustic and acrylonitrile, dried and subjected to mildew, heat resistance tests, and chemical analysis. It was found that the product had reacted to the extent of 0.37 cyanoethyl group per glucose unit, and Was mildew and heat resistant. Thus, 10 days after inoculation with Chaetomium globosum in static culture there was no evidence of mildew growth, whereas the untreated control fabric supported a heavy growth. Also, after heating at a temperature of 320 F. for 20 hours, the untreated cotton fabric had suffered a tensile strength loss of 44.4%, whereas the partially cyanoethylated fabric had a tensile strength loss of only 25.4%.

The invention may also be carried out by treating yarn or fabrics on the dye tubes, for example, of a Gaston County package dyeing machine. In using a one-pound machine, for example, with 1% inch dye tubes on which the cotton is wound, the tubes are placed in the machine which is then closed and the valves adjusted for the dyeing cycle, 5500 ml. of sodium hydroxide of the desired concentration was introduced through the expansion tank. When treating finished goods, such as kiered fabrics, it is advantageous to include in the steeping solution a suitable wetting agent, such as Tergitol P28 (sodium di (Z-ethylhexyl) phosphate) or Aerosol- OS (isopropyl naphthalene sodium sulfonatey. This sodium hydroxide solution containing 0.1% Tcrgitol P-28 was circulated through the fabric for fifteen minutes, reversing the flow of the liquid every two minutes. Then the sodium hydroxide solution was drained, and the package rcmoved from the dyeing machine. It was placed in the centrifuge specifically designed for a single dye package and centrifuged for two minutes to give a caustic pickup of 70-100%.

The fabric package was then returned to the dyeing machine and the machine was adjusted to the drying cycle in which air is forced through the cotton. In this variation of our process the vapors of acrylonitrile are circulated through the steeped cotton fibers in substantially 1 the=same-manner that air is circulated' for drying, the principal diiference beingone of-temperature-toprevent' undue-condensation of-the-acrylonitrile. After the re action-has been carried to'the desired extent, thecirculati'on of'acrylonitrile-is stopped; a solution of- 'aceticacid in water is circulated through the fibers to" new tralize the sodium hydroxide'and simultaneuoslycold water is circulated through the dyepot jacket to reduce- Cotton yarns may be similarly cyanoethylatedandin" practice this is the preferred form for the equipment employed, although it.may.also. be. usedon bulkfibers with theproper machine. adapter.-

We have determined. during. our extensive investigations that as the nitrogen content of the cyanoethylated fabric. increases, the. percentage lossinstrength during soil burial decreases. This relationship'seems to. hold regardless of the reaction conditionsrequired to obtain a given nitrogencontent when dilute sodiunrhydroxide is employed in the presteep. It has been found, however, that the minimum nitrogen content for immunity to attack varies with the construction and weight of the fabric. The reaction conditions in our process which make use of 0.25% to 2% sodium hydroxidesolution as the presteep, and the reaction conditions with acrylonitrile such as will give a nitrogen contempt-2.5% to'4.5% or greater yielda satisfactory product. Some data obtained indicates that for a given, nitrogen content the fabric presteeped with a sodiumhydroxide solution of a concentration less than 1% has :the greatest resistanceto microorganism attack. For example, when cotton fabric was'treated with solutions of 0.25%, 2.0% and 10% sodium hydroxide and cyanoeth-ylated to-fix 2.5% of nitrogen, and the samples given identical soil burial tests at 28 C. for two weeks the loss in tensile strengthv for the three samples was 7%, 10% and'16%, respectively.

Cyanoethylatedcotton fabric with nitrogen contents greater than 3% give satisfactory abrasion resistance as determined on the Stoll abrader. abrasion test, abrasion resistance progressively increases with increasingnitrogen content. On the other hand, flex abrasion resistance progressively decreases until a nitrogen content of 2.5% to 3.0% is reached, after which the decrease becomesprogressivelysmaller. At about 4.5% to 6.0%nitrogen the flex abrasion resistance of the cyanoethylated fabrieis only about 10% to 20% less than that of the untreated cotton fabric.

The resistance of cyanoethylated cotton fabric to, dc.-

gradation by heat progressivelyincreases with increasing nitrogen content. At equal nitrogen contents, cyanoethylated cotton fabric presteeped with sodium hydroxide solutions of less than 1% concentration and cyanoethylated at high reaction ,temperatureshave the greatest resistance to. degradation by heat. By way of example, cotton fabric prcsteeped with 0.1% sodium hydroxide and cyanoethylated to a nitrogen content of 2.0% gave astrength loss of 31% after heating for hours at 160 C. When cotton fabric which was presteeped in a sodium hydroxide solution of 1.25%. and cyanoethylated to a nitrogen content of.2.0% it lost 60% in. strength in a similar test.

Cyanoethylated cotton fabrics with nitrogen contents in the range of 2.0% to 2.5% have the greatestafiinity for many direct and vat dyes. The aflinity for acid and acetate dyes increases with increasing nitrogen contents. The dye afiinity of cyanoethylated cotton fabric thus depends upon the class of dye and perhaps on other dye characteristics which have not been identified. For'many dyes; the rate of dyeing is'increased, the extent of 'dye bathexhaustionis increased and'the color' yield is increased (bythis is meant; a darkersh'ade-is obtained with the"cyanoethylatedcotton for thesame dye pickup than with untreated cotton) Thefabric'was-then In the'case of the flat.

From publishedwork on cyanoethylated cotton, it would b'e anticipated that the affinity ofcyanoethylated cotton for acetate dyes would increase with increasingnitrogen contena Likewise; it would be expected-that 5 the affinity for aeiddyes would improveas the nitrogen contentincreased. On -the other'haud, it'would not be anticipated thatth'e afii'nity' of cyanoeth'ylated 'cottonfor direct, vat; naptholand developed dyes wouldb'e increased as the nitrogen content increased.

The mosteconomical, and hence practical, condition-s product formation increases, long reaction times-are -not-- economical. In general, a-two to three-minutereaction time is preferable, and periodsof time longer than thirty -minutes appear to beundesirabl; By using acrylonitrile in vapor phase, one-can efieet a precisely controlled reaction at a comparatively high temperature.

We have determined thatthe extentand rate of 'reaction of the presteeped cotton fabric with acrylonitrile at a given sodium hydroxide pickup increases with temperature. This is an eif'ect that would nct'have been anticipated. in cellulose chemistry the extent of swelling of cotton with sodium-hydroxide increaseswith-sodium hydroxide concentration and-also increases as the ten1- perature is' lowered. T he. conversion of crystalline cellulose toamorph'ous cellulose followsth'e swelling'behaviour pattern. The extent of cyanoethylation should thus increase when the sodium hydroxide presteep conditions favoring the conversion of crystalline to amorphous cellu lose are used. In the present instance the reverse of this'is' found; that is, increasing the temperature, which would be expected to decrease the extent-of swelling, causes an increase-in the rate and extent of reaction with acrylonitrile. Thus, at temperatures below 46 C., it isimpossible to get a nitrogen content above about 2.2%, which is insuflicient for good mildew andheat resistance. By raising the temperature the nitrogen content leveling off point of the reactionis increased. This dependence on temperature to achieve the desired products is' tin-important and surprising feature of the in vention.

This application is a continuation-impart of our copending application'Serial No. 201,063, filed December 15, 1950; now abandoned;

We claim:

1. The process of treating native cotton fibers to. effect but a partial cyanoethylation of the cellulose and retain the natural physical structure of the fibers which comprises immersing said cotton fibers in an aqueous solutioncontaining from 0.10 to 10% of sodium hydroxide to sorb on the'cellulose from 1.5 to 22'milligrams of sodium hydroxide per granrof cotton, removing from the cotton substantially all the adhering liquid solution, and reacting the cotton while containing the said sorbed amount of sodium hydroxide with acrylonitrile inthe vapor. phase at a temperature of from 46 C. to'85 C. and for a period not-to exceed 4 hours until thereis such an amount of cyanoethylation that the cotton contains from 0.50% to 6.5% of nitrogen based-onthe weightof the cyanoethylated cotton, and retaining the crystalline structure of the cotton fibers substantially unaltered.

2. The. process of claim 1 wherein the sodium hydroxide solution contains from 0.10% 'to 1.75 --of sodium hydroxide.

3. The process of claim 1.wherein the extent of cyanoethylation is such that the cotton contains fr0m'0.50% to' 4.30% nitrogen based on the weight of the cyanoethylated cotton.

4. The-process of-claim1 whereinthe aqueous solu tion of sodium hydroxide in which the cotton is immersed contains from 0.1% to 1.75% sodium hydroxide at a temperature of from about 45 C. to 50 C. and the reaction with acrylonitrile is from about 1.5 to 90 minutes to cyanoethylate only the amorphous portion of the cotton.

5. The process of treating native cotton fibers to effect but a partial cyanoethylation of the cellulose and retain the natural physical structure of the fibers and produce a product having exceptional resistance to micro-organism degradation, which comprises presteeping native cotton fibers in an aqueous solution containing from 0.25% to 1.75 of sodium hydroxide to sorb on the cellulose from 1.5 to 22 milligrams of sodium hydroxide per gram of cotton, removing from the cotton substantially all of the adhering liquid solution, reacting the presteeped cotton while containing said sorbed amount of sodium hydroxide with acrylonitrile in vapor phase at a temperature of from 71 C. to 76 C. until the amorphous portion of the cotton fibers form cyanoethyl-cellulose in such amount that the nitrogen content varies from 2.5% to about 6.5% based on the weight of the cyanoethylated cotton, and retaining the crystalline structure of the cotton fibers substantially unaltered.

6. The process of claim wherein commercial acrylonitrile which contains some water is used for reaction with the presteeped cotton and the vapor is at a temperature near the boiling point of the azeotrope which is about 71 C. to 72 C.

7. The process of treating native cotton fibers to efiect but a partial cyanoethylation of the cellulose and retain the natural physical structure of the fibers which comprises impregnating the native cotton fibers with an aqueous solution containing from 0.10% to of sodium hydroxide for a period of time suflicient to sorb on the cotton from 1.5 to 22 milligrams of sodium hydroxide per gram of cotton, removing from the cotton substantially all of the adhering liquid solution, and reacting the cotton while containing said sorbed amount of sodium hydroxide with acrylonitrile in vapor phase at a temperature of from 46 C. to 85 C. in a chamber to effect cyanoethylation with but the amorphous portion of the cotton, removing the cotton from the chamber, and maintaining the cotton at said temperature range to react the residual acrylonitrile vapor with the cotton, said cotton containing from 0.50% to 6.5% nitrogen based on the weight of the cyanoethylated cotton and having the crystalline structure of the cotton fibers substantially unaltered, whereby said cotton has the hand and appearance of natural cotton but is highly resistant to microorganism degradation.

8. The process of claim 7 wherein the cotton treated is an article in the form of yarn, cord, and fabric, and is passed continuously through the process, first through the sodium hydroxide solution, then while the cotton is at a temperature of about 75 C. removing excess solution and furthering the reaction with the cotton, then through the acrylonitrile vapor, and then washing and drying the article.

9. The process of claim 7 wherein the native cotton fibers are passed through the sodium hydroxide solution and then the cotton is passed through a chamber containing acrylonitrile vapors until there is such an amount of cyanoethylation that the cotton fibers contain from 0.77% to 4.30% of nitrogen based on the weight of the cyanoethylated cotton.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE PROCESS OF TREATING NATIVE COTTON FIBERS TO EFFECT BUT A PARTIAL CYANOETHYLATION OF THE CELLULOSE AND RETAIN THE NATURAL PHYSICAL STRUCTURE OF THE FIBERS WHICH COMPRISES IMMERSING SAID COTTON FIBERS IN AN AQUEOUS SOLUTION CONTAINING FROM 0.10 TO 10% OF SODIUM HYDROXIDE TO SORB ON THE CELLULOSE FROM 1.5 TO 22 MILLIGRAMS OF SODIUM HYDROXIDE PER GRAM OF COTTON, REMOVING FROM THE COTTOM SUBSTANTIALLY ALL THE ADHERING LIQUID SOLUTION, AND REACTING THE COTTON WHILE CONTAINING THE SAID SORBED AMOUNT OF SODIUM HYDROXIDE WITH ACRYLONITRILE IN THE VAPOR PHASE AT A TEMPERATURE OF FROM 46*C. TO 85*C AND FOR A PERIOD NOT TO EXCEED 4 HOURS UNTIL THERE IS SUCH AN AMOUNT OF CYANOETHYLATION THAT THE COTTOM CONTAINS FROM 0.50% TO 6.5% OF NITROGEN BASED ON THE WEIGHT OF THE CYANOETHYLATED COTTON, AND RETAINING THE CRYSTALLINE STRUCTURE OF THE COTTON FIBERS SUBSTANTIALLY UNALTERED. 